SFTP

SFTP (SSH File Transfer Protocol) is a protocol for securely transferring and managing files within an encrypted SSH connection. It lets you not only upload and download files but also browse, rename, delete and set permissions on them — all over a single encrypted channel on port 22. Despite the similar name, it is not an extension of classic FTP but a separate protocol built on top of SSH.

How SFTP works

SFTP relies on SSH mechanisms to establish and protect the session:

1. the client connects to the SSH server and authenticates — by password or, more securely, with an SSH key,
2. once the encrypted tunnel is up, the SFTP subsystem is started,
3. commands and data (transfers, directory listings, permission changes) all flow through that single encrypted channel.

Because the entire exchange is encrypted, neither the login, nor the password, nor the transferred files are exposed to interception in transit — unlike plaintext FTP.

SFTP in practice

SFTP is the standard for securely uploading files to a server: deploying websites, publishing application files, moving backups, or exchanging data between systems. It is used through clients such as FileZilla and WinSCP — the latter often paired with PuTTY — as well as from the command line (sftp user@host). On modern hosting and VPS servers, SFTP is the default, recommended way to access files, replacing outdated, unencrypted FTP wherever transmission security matters.